Currently, high pressure gas generators (such as a vapor boiler) use diesel oil, heavy oil, coal, charcoal, etc. to heat water so as to generate vapor. Then the heat energy from the vapor is used to drive a machine (such as a gas turbine, a generator, etc.). The prior art high pressure gas generators have complicated structure, and a bulge volume, and is difficult to be maintained. Furthermore the fuels used (such as diesel oil, heavy oil, coal, charcoal, etc.) are low efficiency so that some energy is lost.